Method of making armor-plate.



LEE H. BOWMAN, OF MUNHALL,

ATNT are.

PENNSYLVANIA, ASSIGNOR TO CARNEGIE STEEL I COMPANY, OF PITTSBURG, PENNSYLVANIA, A CORPORATION OF NEW JERSEY.

METHOD OF MAKING- ARMOR-PLATE Specification of Letters Patent.

No Drawing. Application filed May 18,-1908, Serial No. 433,499.

To all whom it may concern:

Be it known that I, LEE H. BOWMAN, of Munhall, Allegheny county, Pennsylvania, have invented a new and useful Method of Making Armor-Plate, of which the following is a full, clear, and exact description.

My invention relates to the manufacture of'face hardened armor plate and is designed to provide an improved method by which the back portion of the plate is given a greater tensile strength than that present in the plates as nowmade.

The invention consists primarily in subjecting the back portion of the plate to a be converted into fiber which gives a struc- The plate should be given a longer heat ture of higher tensile strength than that now afforded to present plates.

In carrying out my invention, I prefer-'- ably follow standard practice in casting and forging, ,after which the, plate maybe carburized and reforged or not as desired, and then fiber the plate in the ordinary manner by heat treatments, such as are well known. The plate may then be shaped and machined if desired. At this point I then introduce my new step, which step preferably consists in bedding the face portion of the plate in loam, introducing the plate into a furnace, and heating the back of the plate up to a temperature of about 950 C. This heat should be carried to above the point of recalescence and may be varied above such temperature according to the chill desired.

treatment than that now used for face-hardening or the temperature should be in creased. In this step, the back and preferably about half of the body of the plate, is brought to a high temperature, or above the point at which steel burdens, after which the plate is taken out of the furnace and quenched, preferably in water. The back of the plate is then given the crystalline structure which may extend to any desired depth, preferably to about half the thickness of the plate. The plate is then face-hardened in any desirable manner, as for example by bedding the back in loam, placing the plate in the furnace and heating its face to about 950 C. During this heat treatment of the face, the back of the plate will be brought up to a temperature of about (3., when the plate is then'taken out and quenched, preferably in Water. The crystalline back portion of the plate verted into a strong fibrous structure, while at the same time the face will be given the desired hardness. In this operation, both faces are preferably quenched by water sprays, although they may not be applied for the same duration on each face. If the temperature of the back of the plate is slightly higher than desired when the plate is taken out of the furnace, the spray may be applied to the face ofthe plate, and when the back has been. brought down to the proper temperature the spray is then applied to it.

The advantages of my invention result from the steps of forming a crystalline structure on the back portion of the plate and then converting this structure into astrong, fibrous structure. It is found in practice that this increases the ballistic rewill be consistance of the plate. The crystalline structure of the back portion of the plate may be converted into fiber either during the face hardening or before it.

While my process is applied advantageously to face-earburized armor plate, it may be applied to homogeneous plates, in which case the homogeneous back wouldv be converted into a strong fiber back by heat treatment.

I claim 1. In the manufacture of armor plate, the steps consisting in taking a fibered steel plate, heating the back portion of the plateto convert it into a crystalline structure while retaining the face portion in annealed or fibered condition, quenching the same,

and then converting said crystalline structure into a strong, fibrous structure by heat treatment and quenching; substantially as described.

2. In the manufacture of armor plate, the steps consisting in forming a fibered steel plate, heating the back portion of the plate up to above the recalescence point While relnini-ng the face portion in annealed or fiber-ed condition, quenching the plate, then heating the face portion to above the reand then quenching to produce a crystalline calescence point While the back portion of structure in said back, and then converting 15 the plate is heated to a temperature not exthe crystalline structure of the back into a ceeding that at which annealing takes place strong fibered portion by heating the face 5 and then quenching the plate to convert the portion of the plate to the proper hardening crystalline structure -of the back into a temperature and quenching the plate; substrong fibrous structure; substantially as destantially as described. 20 scribed. In testimony whereof, I have hereunto set 3. The method of making face hardened my hand. -10 armor plate, consisting in heating the back LEE H. BOWMAN.

portion of a fibered or annealed plate to the Witnesses: proper temperature While retaining the face G. M. VLERS, portion in annealed or fibered condition, H. M. CORWIN. 

